Factor VIII and von Willebrand's factor are associated plasma proteins that together are called Antihemophlic Factor (AHF). Both are important in the blood clotting mechanism. Factor VIII serves as a co-factor along with calcium and phospholipid to enable Factor IX.sub.a to cleave zymogen Factor X to thus activate Factor X, all being a part of the complex coagulation cascade system. Von Willebrand's factor (vWF) apparently acts in the aggregation of platelets which provide the necessary phospholipid. The absence of either of these factors may result in prolonged bleeding times. Factor V also serves an important role in the coagulation system by aiding activated Factor X in the cleavage of prothrombin to thrombin. (The Plasma Proteins, Vol. III, 2nd Ed., Structure, Function, Genetic Control (1977) (Academic Press, Inc., N.Y.) p. 422-544.)
Several methods of making concentrates of AHF are in current use. These range from simply freezing and then thawing plasma (cryoprecipitation) to yield a more concentrated insoluble mixture of Factor VIII, fibrinogen, cold-insoluble globulin to more involved procedures, etc. These concentrates may be made more highly purified by further treatment employing techniques such as aluminum hydroxide absorbtion, glycine extraction, polyethylene glycol concentration, filtration, etc. Difficulties associated with these highly purified concentrates may for example include a loss of the Factor VIII clotting activity and/or an increase in the percentage of unwanted alloagglutinins. (I. M. Nilsson; L. Holmberg; P. Seenberg; P. Menrichson, Scand. J. Haematology 24: 340-349 (1980), Allain, J. P.; F. Vervoust; J. P. Soulier, Vox Sang. 38: 68-80 (1980).